The use of personalized audio reproduction has become increasingly widespread with the advent and popularity of portable communication and audio reproduction devices resulting in personalized audio provision in public and shared environments becoming frequent.
In order to provide personalized audio, earphones of some form are typically used. For example, a set of headphones may comprise an earphone for each ear which e.g. may be an in-ear earphone or a closed earphone design surrounding the user's ears. Another example of the use of earphones for providing personalized audio is the use of hearing aids e.g. by hearing impaired users.
Many such earphones are arranged to also provide a passive attenuation of external ambient noise. For example, a well-designed in-ear earphone may reduce the external noise with approximately 25 dB due to the acoustic seal between the ear canal and the acoustic environment. Similarly, out-of-ear closed earphones may also provide a substantial passive attenuation of the external environment, especially for high frequencies.
Such noise reduction may be advantageous in many scenarios. For example, for far-end communication (e.g. over a phone link) in noisy environments, it is preferable to reduce external noise that tends to reduce the intelligibility of the far-end party. As another example, listening to music in noisy environments also tends to be more pleasant when the external noise is reduced, for example in airplanes, busses, trains and crowded public places.
Further, closed or in-ear earphone designs may not only provide attenuation of the external sounds but may also provide an improved quality of the rendered audio due to the close coupling between the earphone and the user's ear. Indeed, in many cases, the closed or in-ear design may be selected due to the audio quality that can be achieved for a given size of the earphone.
However, in many scenarios the attenuation of the external sounds may be disadvantageous. For example, it may not only attenuate undesired noise but may also attenuate desired external sounds.
As an example, the wearing of closed or in-ear earphones in traffic and other situations where attention to the acoustic environment is important may be impractical and indeed the reduction of the external sounds may even lead to dangerous situations. Also, the use of such earphones results in an occlusion effect that is similar to the experience when the ears are blocked (e.g. by water). The occlusion effect drastically reduces the sense of comfort as the ear feels blocked and substantially affects the perception of the user's own voice resulting in a perceived distortion.
As the same earphones are typically used in many different scenarios, the earphone is likely to be suboptimal in some scenarios, and indeed in some scenarios an earphone is likely to not provide enough external sound to the user and in other scenarios it is likely to provide too much external sound to the user.
In order to improve the perceived quality and user experience for a given earphone, a number of signal processing algorithms for processing the signal to be rendered by the earphone have been suggested. For example, active noise cancelling where a microphone measures an ambient noise signal which is used to generate an inverse phase cancelling sound signal from the sound transducer of the earphone has been proposed. As another example, for closed or in-ear headphones, it has been proposed that a microphone may capture external sounds and add these to the sound being reproduced.
However, although such algorithms for modifying the sound reproduced by the sound transducer of the earphone may provide improved performance in many scenarios, they also tend to be suboptimal in some situations and in particular may not provide full flexibility for optimization. Indeed, in some scenarios such approaches may provide a suboptimal audio quality or user experience. The approaches also tend to be relatively complex and to result in increased cost of the earphone system.
Hence, an improved approach would be advantageous and in particular an approach allowing increased flexibility, improved dynamic adaptation to different audio environments and/or use scenarios, improved perceived audio quality, reduced complexity, facilitated operation, facilitated implementation and/or improved performance would be advantageous.